The aircraft has been getting bigger recently and its body has several hundred seats in practical use. Since many lives are lost in case of aircraft crash, very strict quality management is to be performed at the time of manufacturing the aircraft. This strict quality management is implemented not only for the manufacturing processes of the body of the aircraft but also for each machine element product contained in the engine and the like in the aircraft.
In addition, an aerospace equipment is originally required for traceability in which the history, application or whereabouts of an object to be considered is traceable. This is because when the aerospace equipment has an accident, it is necessary to immediately specify its cause and when there is a defective in a machine element product, it is necessary to immediately specify and exchange the defective part.
Regarding each machine element product of the aircraft, as for a bearing used in a jet engine for example, its material, its machine tool and the skill of an engineer have to be qualified every machine element and when any of them is not qualified, the machine element cannot be delivered.
This quality management is necessary for not only the aircraft containing a flying object such as a fixed wing, a rotating wing and a missile, but also for a space appliance including a rocket, a rocket engine, and an artificial satellite.
The machine element product is mainly managed as follows.
First, as for the material, a process lot number of material showing the material constituent or the furnace in which the material is manufactured, a specification number and a revision letter are managed. The revision letter represents the number of times of the revision from the original specification. As for turning/forging, a time, a place and a facility in which the process is performed and its processing condition are managed.
As for a heat treatment, a specification number and a revision letter in a specification in which a temperature condition and the like are determined and a heat treatment condition are managed. As for grinding, a time, the machine used and its condition are managed. As for a surface treatment, the kind of the surface treatment, a specification number and a revision letter and the like are managed. As for an inspection, a nondestructive inspection is mainly conducted, and the kind of the nondestructive inspection, a specification number and a revision letter and the like are managed. As for rust-preventing and packaging, the kind of a rust-preventing oil or packaging, a specification number and a revision letter and the like are managed.
According to the quality management for each machine element product, although the component such as a ring, a rolling element, a retainer or the like is forged, heat treated and ground by the lot, the completed machine element product is not managed by the lot but it is managed individually.
As to the quality management method in which the above manufacturing history is clarified, the information is conventionally recorded on a document and stored in general, and when the customer requests the information, the document has to be managed so that the same is immediately provide to the customer. Moreover, as long as the machine element product is used, the document has to be stored for a long period of time, so that the stored documents become enormous at the quality management section in the manufacturer and space for the documents is needed.
In order to reduce the document amount, measures such that the information generated at each process is inputted to the computer terminal accessible to a database and the like are taken, but actually, the information is stored in the document to backup the information in view of the risk of data extinction.
Meanwhile, an IC tag is coming to be used in physical distribution management or inventory management. For example, management through the manufacturing to abandonment stages using the IC tag in the manufacturing of a product such as a car is proposed in the above Japanese Unexamined Patent Publication No. 2002-169858. Since information can be recorded and read to and from the IC tag without contact and the storage capacity of the IC tag is large, high degree of management can be expected.
According to a conventional example of the quality management method using the IC tag, various kinds of information about a machine element product is directly recorded on the IC tag attached to the machine element product, or identification information is recorded on the IC tag and material and lot management information and various kinds of history data and the like about the machine element product is provided by making reference to a database.
However, the cause of a defect generated in the machine element product cannot be specified with the information about the machine element product only in some cases. For example, a difference in quality is generated by a difference in processing condition at each process and such difference caused by the difference in processing condition cannot be recognized from the inspected result in some cases. Since the machine element product such as the rolling bearing and the like comprises a plurality of components, even when the inspected result of the assembled machine element product itself and the like can be known, a defect caused by the difference in quality of each component cannot be specified.
Especially, in the case of the machine element product having a rolling element of a rolling bearing and the like, since a slight difference in material and precision leads to a great difference in performance of the machine element product, which is hard to deal with in the conventional example of the quality management method using the IC tag.
Furthermore, as for process management, according to the conventional management method in which the information is written on the slip or inputted to a terminal every process, the writing and inputting are troublesome, so that it is difficult to record various kinds of information in detail. Especially, according to a machine element product constituted by assembling a plurality of components like the rolling bearing in which components are produced through material purchase, a forging process, a heat treatment process, a grinding process and a surface treatment process, by the lot every process, the management at the manufacturing processes of the component is complicated and it takes a lot of trouble to handwrite and input the information. Therefore, it is difficult to sufficiently answer the request for detailed history information about the machine element product and management cost becomes high.
Thus, it is considered to use the IC tag. However, the management for the product such as a car cannot be applied to the above machine element product. According to the above Japanese Unexamined Patent Publication No. 2002-169858, the IC tag is attached to the car that is an object to be managed and information about each process is recorded on the IC tag. The IC tag is attached to a frame and the like.
However, according to the machine element product such as the rolling bearing, since there is no completed reference component like the frame in the car and each component is manufactured through a forging and heat treatment processes in the manufacturing process, the IC tag cannot be attached to the machine element product itself In addition, according to the machine element product such as the rolling bearing, since each of an inner ring, an outer ring, a rolling element and the like is managed through the material purchase, the forging process, the heat treatment process, the grinding process and the surface treatment process, when the IC tag is to be used in the quality management, it is difficult to decide how to use it specifically and use it effectively.